Catheters or elongated working channels are a staple device in performing noninvasive medical procedure. The advantages of noninvasive procedures are numerous and include decreased risk of infection, decreased tissue damage, and shorter recovery periods. Unfortunately, the types of procedures that can be preformed utilizing noninvasive techniques is often limited by the size of the body lumen through which the procedure will be conducted and, to an equal extent, the size of the catheter or working channel inserted into the body lumen through which the tools for conducting the procedures will be passed through.
Catheters or elongated working channels are often supplied in standard sizes specific to a particular medical field or application. For example, in procedures involving the lung or bronchial tree, a bronchoscope is typically employed to span from the mouth, through the trachea, to proximal locations in the primary branches of the bronchial tree. Bronchoscopes generally have within their structure a working channel through which devices may be passed to access and perform procedures within the lungs. This working channel typically has an inner diameter of 2.8 mm. Therefore, all noninvasive pulmonary procedures utilizing a bronchoscope are limited to employing only those tools and devices that can fit within a 2.8 mm working channel.
Due to the size limitation of the bronchoscope's working channel, it is often necessary for a physician to pass a first tool or device through the working channel, retract the first device, pass a second device through the channel, and repeat this process several times with either the same or different devices. This method not only lengthens the procedure time but also introduces the possibility that the bronchoscope or elongated working channel through which devices are passed may migrate from their desired locations.
This limited working channel diameter not only dictates the size of the tools and devices a physician can use but also the size of tissue samples that may be obtained from a patient. Again, in the case of bronchoscopes, in order to obtain a sample of tissue at a point of interest, an extended working channel is typically passed through the working channel of the bronchoscope and positioned proximate to the point of interest. The extended working channel (or “EWC”) is a catheter having an outside diameter of less than 2.8 mm. A biopsy needle is then passed through the EWC, used to extract the sample, and retracted from the channel. Because the EWC has an outside diameter of less than 2.8 mm, it follows that the inside diameter of the EWC is significantly smaller. Due to the limited diameter of the EWC, the biopsy device will necessarily be quite small. As a result the tissue sample obtained will also be very small. The limited size of the tissue samples that can be obtained in this manner, in turn, often necessitate repeating the tissue extraction and sampling process several times in order to obtain a reasonable representation of the tissue characteristics within the area of interest.
In the case of bronchoscopes, the 2.8 mm diameter limitation is not dictated by the constraints and characteristics of the bronchial tree. To the contrary, the tissue forming the airways of the bronchial tree are quite elastic, distal of the cartilagenous zone. These lumens are safely, and easily expanded and capable of receiving catheters and elongated working channels of significantly greater diameters than currently used. The risk of trauma does not arise from radially stretching the airways. Rather, injury is more likely to be caused by longitudinally advancing a relatively large, less flexible device through the airways, thereby placing undue axial, rather than radial, pressure on the airways and branches.
There is a need in the field for a catheter or EWC that can be initially passed through the working channel of a conventional endoscope, bronchoscope or similar device but that upon placement, may radially expand once deployed within the body lumen. Thereby providing a elongated working channel through which a physician may simultaneously pass multiple tools or devices, larger tools or devices, and extract larger tissue samples.
Ideally, this EWC would also be locatable by a three-dimensional navigation system. The working channel of a bronchoscope ends at the distal end of the bronchoscope, which is also where the lens of the scope is located. The working channel allows a physician to access tissue with a tool while watching the tool through the scope. Using an EWC however, often extends the tool past the viewing range of the scope. This is especially true in the lungs where the airways narrow quickly, preventing the use of the scope in the distal airways.
Three dimensional tracking technology has allowed an EWC to be safely and accurately navigated into the distal airways, well past the reach of the bronchoscope. This tracking technology typically utilizes a small location sensor, preferably providing tracking data in six degrees of freedom, at a distal tip of a probe. Suitable sensors, sensing techniques and related methods and devices are disclosed in U.S. Pat. Nos. 6,188,355; 6,226,543; 6,558,333; 6,574,498; 6,593,884; 6,615,155; 6,702,780; 6,711,429; 6,833,814; 6,974,788; and 6,996,430, all to Gilboa or Gilboa et al.; and U.S. Published Applications Pub. Nos. 2002/0193686; 2003/0074011; 2003/0216639; 2004/0249267 to either Gilboa or Gilboa et al. All of these references are incorporated herein in their entireties.